This invention relates to an internal combustion engine equipped with an exhaust gas purifying system.
In general, in the exhaust gas purifying system in which a catalytic converter is provided in an exhaust system to diminish noxious components in exhaust gas, it is desirable to set and maintain an air-fuel ratio of a mixture supplied to a combustion chamber of the engine close to a stoichiometric air-fuel ratio so as to improve an efficiency of purification of the exhaust gas within said catalytic converter. It is preferable to maintain the air-fuel ratio of the mixture at about the stoichiometric air-fuel ratio .+-.0.1 in order to have the noxious components such as NOx, HC, CO reduced or oxidized simultaneously by for example a ternary catalytic converter.
As a mixture supplying device for setting and maintaining the air-fuel ratio of the mixture at about the stoichiometric air-fuel ratio, it has been proposed and utilized an electronic-controlled fuel injection system which injects into an intake passage an amount of fuel controlled in proportion to said set air-fuel ratio with respect to an amount of the inducted air by means of an electronic control circuit. However, such system is very expensive and maintenance thereof is difficult.